The present application relates to a variable focal length lens, a camera module, and an electronic apparatus, and more particularly to a variable focal length lens using a liquid medium as a light refracting medium, a camera module and an electronic apparatus including the variable focal length lens.
In imaging apparatus, such as still cameras and video camcorders, and camera modules built in mobile phones, one of the challenges has been reducing the size of an imaging lens optical system. On the other hand, in such imaging apparatus and camera modules, one of the highly requested functions is a focal length changing function, what is called an optical zoom function.
In an existing imaging lens having an optical zoom function (hereinafter referred to as a zoom lens), however, the focal length is changed by moving a plurality of fixed focal length lenses made of glass, resins, or any other suitable materials in the zoom lens in the optical axis direction. The existing zoom lens therefore typically requires providing a lens moving space therein, resulting in difficulty in size reduction. That is, in an existing imaging apparatus or camera module, adding an optical zoom function and reducing the size of the imaging lens optical system are tradeoffs.
To solve the problem described above, it is conceivable to use a variable focal length lens as the zoom lens. Forming a zoom lens with a variable focal length lens eliminates the need for a lens moving space in the zoom lens, solving the problem described above.
As a variable focal length lens of this type, a variable focal length lens using liquid as a light refracting medium has been proposed (see JP-A-2000-81504, for example). In the variable focal length lens proposed in JP-A-2000-81504, the lens surface is deformed to adjust the focal length by applying pressure to a container in which liquid is sealed to deform the liquid.
In another technology having been proposed, an existing variable focal length lens using liquid as the refracting medium is used in a wide converter (see JP-A-2008-185627, for example). JP-A-2008-185627 proposes a method for deforming the lens surface by driving, for example, an external pump mechanism to change the amount of liquid with which the variable focal length lens is filled.